Method of grinding



April 1958 E. v. FLANDQERS Re. 24,448

METHOD OF GRINDING, INCLUDING GRINDING FORMING Original Filed Nov. 20.1953 2 Sheets-Sheet 1 I April 1, 1958 E. v. FLANDERS Re. 24,448

METHOD OF GRINDING, INCLUDING GRINDING WHEEL FORMING 2 Sheets-Sheet 2Original Filed Nov. 20, 1953 I JizZ/IZE l zzm 40 4 gunman IIIIIIIIIIIIIIUnited States Patent Office Re. 24,448 Reissued Apr. 1, 1958 METHOD OFGRINDING, INCLUDING GRINDING WHEEL FORMING Ernest V. Flanders, by Jonesand Lamson Machine Company, Springfield, Vt., assignee Original No.2,778,170, dated January 22, 1957, Serial No. 393,260, November 20,1953. Application for reissue October 21, 1957, Serial No. 693,500

Claims. (Cl. 51-283) This invention relates to new and usefulimprovements in grinding machines, and relates more particularly tonovel means for shaping the periphery of grinding wheels to a desiredform.

Heretofore, grinding wheels have been dressed by either of two methods:(1) roller crusher dressing; and (2) diamond dressing. In roller crusherdressing it is common practice to press a roll of steel or othersuitable material firmly against the grinding wheel, and positivelydrive the roll or wheel at a relatively slow speed. The grinding wheelor roll is thus driven at substantially the same peripheral velocity,and the roll acts in such a way as to crush or pulverize the grindingwheel grains to thereby produce on the wheel a complement of the crusherroll shape. This method is satisfactory in many cases, particularly onwork not requiring the utmost in precision and finish. However, it isnot possible to crush dress the many so-called resinoid. or rubberbonded abrading wheels. Such wheels cannot be broken down or pulverizedsuccessfully to desired forms by a crushing process. In diamonddressing, a diamond tool is applied to the wheel and guided in such apath as to produce a desired form on the wheel. Many mechanisms havebeen proposed for the accurate location and precision movement of thediamond tool. cutting on a lathe or similar machine tool, and isnormally done at speeds higher than. crush dressing speeds, yetsubstantially lower than actual work grinding speeds. Typical crushingspeeds may be in the order of only 400 peripheral feet per minute;diamond truing speeds may be in the order of 2000 peripheral feet perminute; whereas actual grinding is usually done at speeds of 8000 feetper minute or'higher in modern high level production.

On anyknown grinding machines, therefore, actual production must beinterrupted periodically for a wheel dressing operation, whether it beperformed by crusher roll or diamond tool. This operation requires aslowdown of the wheel to wheel truing speeds, and after the dressingoperation takes place, the wheel must be accelerated back to grindingspeeds. This process, it can readily be appreciated, is time-consumingand therefore costly.

In accordance with this invention, I propose a new method of formingwheels which overcomes the difliculties described briefly above andwhich provides great advantages as will be pointed out hereinafter. V

' A further object of my invention is to provide a method of wheelforming suitable for all types of wheels regardless of the bond or gritemployed, and to a degree of accuracy equal to that achieved by the bestconventional method r These and other objects and advantages of myinvention will become readily apparent from the following specificationsand drawings, in which The action is rather analogous to Figure 1 is aview in elevation of wheel forming apparatus embodying my invention;

Figure 2 is a detailed view, partly in section, of a wheel forming rollin contact with a grinding wheel;

Figure 3 is a view on section lines 3-3 of Figure 1;

Figure 4 is a plan view of the apparatus shown in Figure 1;

Figure 5 is a detail of the gear train forming part of the mechanism ofFigure 4;

Figure 6 is a view on the section lines 6-6 of Figure 1;

Figure 7 shows a modification of the forming tool drive mechanism;

Figure 8 is a view on the section lines 8-8 of Figure'7;

Figure 9 is a further modification of the drive mechanism shown inFigure 7;

Figure 10 is a view on the section lines 1010 of Figure 9; t

Figure 11 is a view on the section lines 1111 of Figure 9.

Briefly stated, my invention contemplates the use of tool which may bein the form of a roll made preferably of a hard and abrasive substancelike diamond particles held in a bonding material, or matrix. This rollis formed so as to have on its periphery a complement of the shape whichit is desired to produce on a grinding wheel. The roll is forced againstthe grinding wheel, while the wheel is in rotation under power, and theroll is also rotated or oscillated under power so that successiveportions thereof are brought into contact with the grinding wheel.

he wheel may be in continuous operation, rotating at actual grindingspeeds, and, if desired, may be performing grinding operations evenwhile the wheel form is being maintained at another point on itsperiphery.

Referring more particularly to the drawings, I have shown a portion of agrinding machine suflicieut to illustrate the invention, having a bed 10on which is mounted a grinding wheel slide 11. The wheel slide may bemounted on ways (not shown) for motion radially toward and away from agrinding point on the machine as is well understood in the art. Theslide 11 carries a cylindrical housing 13 which contains the wheelforming mechanism. The arrangement of this housing 13 and itsrelationship to the grinding wheel is somewhat similar to that in U. S.Patent 2,578,531, granted December 11, 1951, to Ernest V. Flanders etal.

Mounted on housing 13 is a motor 14 which may be any suitable constantspeed motor providing power through belts or the like 15 to the shaft16. Through worm 17, the rotation of shaft 16 is transmitted to shaft18, when a dog clutch 19 operated by a solenoid 20 is in the engagedposition. When clutch 19 is engaged, the shaft 18 is driven by the motor14 and this motion is transmitted through gear train 21, 22, 23, 24, 25to a shaft 26.

Through an idler gear 27, best shown in Figure 1, a shaft 28 is rotatedat the same speed as the shaft 26. The shaft 28 is journaled in andmoves with the wheel slide 11.

On shaft 28 is a pinion 29, which drives a lead screw 32 through a widefaced idler 30 and pinion 31. The pinions 29 and 31 are the same size,and therefore it can be seen that the lead screw 32, journaled in thebed 10, the shaft 28, and the shaft 26 (Fig. 4) all rotate at the samespeed when the clutch 19 is engaged. When the clutch 19 is disengaged byenergization of the solenoid 20, the motor 14 merely idles and theentire gear arrangement to the shafts 26, 28 and screw 32 is at rest. Iprovide a cover plate 33 which may be removed for conveniently changingthe gear ratio in the train, best shown in Figure 3. Through changegears any desired rate of rotation of shaft 26 and screw 32 may be ob,In addition to driving the gear train (Figure 3) the shaft 16 has asecond power take-01f portion compris ng a worth 34 and gear 35. Thisgear combination drives a pinion 36 which meshes with a wide faced gear&7.

The gear 37 is on a shaft 38 journaled in the housing 13. I At theforward end of shaft 38 I provide a pair .of bevel gears .40 and 39,best shown in Figure 4, which impart rotary motion to a Wheel formingroll 41. This entire roll driving assembly is slidably mounted inbrackcts 42; A collar 43 is pinned to the shell 44. A threaded hole incollar extension 45 engages a threaded end portion on the shaft 26. Thisthread is of the same pitch as the lead screw 32. A yoke (see Figure 6)slidably en gages retaining pin 46 which supports the collar assembly.

When shaft 26 is rotated, axial motion is transmitted to the collar 43and thus the roll 41 is slowly advanced toward the grinding wheel 12.During this advancing motipn, theroll is continuously rotated throughthe medium of pinion 36 and gear 37, and bevel gears 39, 40.

Since as heretofore explained the lead screw 32 turns with the shaft 26,it can readily be seen that through a nut portion 47 on the wheel slide11 engaging the screw 32, the entire wheel slide also moves in the samedirection and at the same rate as the motion of the roll 41 toward thegrinding wheel. In this manner as the wheel consumed, the working pointon the periphery of the wheel, substantially 180 degrees from the pointof form-' ingroll engagement, remains in proper position relative to thework piece. This constant relationship assures accurate and automaticmaintenance of work size even though the wheel diameter is constantlydecreasing.

Figures 7 and 8 illustrate a modification of the wheel forming assemblyto provide an oscillatory motion to a roll or roll segment. The bevelgears 39 and 40 impart an oscillatory motion to the wheel formingsegment 48 through an adjustable throw eccentric as at 49.

In Figures 9, l0 and 11, I illustrate mechanism for impartingoscillatory straight line motion to a wheel forming tool in the form ofa bar 50. In place of the bevel gear combination 39-40 spur gears 51 and52 drive the bar 50 up and down on ball slide 53 through an adjustablethrow eccentric 54.

: In each case, the portion of the wheel forming tools 41, 48 or 50contacting the grinding wheel is in constant change, while themechanisms heretofore described advance the wheel forming tool againstthe wheel at a relatively slow, predetermined rate. This rate may be altered by proper choice of change gears shown in Figure 3 and varies withthe character of the grinding wheel itself, the type of workpiece, thecomplexity of the wheel form being maintained, and the degree ofaccuracy req red- If the nature of the work is such as to permit severalcomplete cycles with no dressing action, it is merely I necessary toenergize solenoid 20, thus interrupting the advance of the wheel formingmember. This may be done automatically by a cycle counter set to permitengagement to clutch 19 after a predetermined number of work pieces havebeen ground. In any case, the grinding speed is maintained, and no timeconsuming slow-down is necessary to maintain wheel form. In someapplications, Where the grinding process causes rapid wheel wear, as,for example, when operations are being performed on extremely hard orresistant work material, I have found it desirable to leave the clutch19 in continuous engage ment during grinding. Of course, it is desirableto disengage the clutch 19 during the unloading of the finished work andthe loading of a new workpiece to avoid unnecessary wheel consumption.In such a case, the solenoid 20 may be included in an automatic workloading cycle, or interlocked with a Work fixture, chuck or the like tooperate without further attention.

'- I have'found the methods described herein to be effective onresinoicl as well as on vitrified wheels. In conventional crush dressingit is essential to drive the wheel and roll at substantially the samelow peripheral velocity. The random pulverization, elfective only onvitrified wheels, leaves a wheel surface which is inferior to thatproduced by my continuous process carried out at high speeds. Mycontinuous wheel forming process results in a free-cutting, open grainedwheel, yet with a fine structure to insure long life and work of highaccuracy and finish.

Continuous wheel forming in accordance with this invention is mostadvantageous in that it enables the user to combine high accuracy with ahigh rate of production. Heretofore, maximum stock removal rates couldnot be employed where the grinding wheel broke down between the startand the finish of the grinding operation on a single workpiece. Heavycuts resulted in wheel breakdown which was enough to cause a loss ofaccuracy. In the typical case the form produced would deviate from thedesired standard before the operation was finished. In grinding a wormgear from the solid, for ex ample, the initial turns of the thread wouldbe correctly formed, but the last threads would be of reduced depthbecause of wheel breakdown and finish would be impaired because of thedeclining efficiency of the grinding stock and produce acceptable work.This method of approach, while achieving the desired end, is timeconsuming and therefore expensive.

In continuous wheel forming as taught herein, on the other hand, thehigh stock removal rates (heretofore achieved on roughing cuts only) cannow be realized with the heavy cuts producing the final desired form onthe workpiece. The grinding wheel is continuously corrected so that thelast part of the grinding pass is accomplished with the same accuracyand efliciency as the first part of the grinding pass. Thus wheel truingtime is not added to total time expended. Furthermore, work usuallyrequiring two or more passes is now finished in a single cuttingoperation.

The time savings are spectacular and of particular importance in modernmass production where standards of accuracy are becoming higher. It isbecoming necessary to achieve close grinding tolerances on more and moreparts, and continuous wheel forming with automatic size control hasproven to be a significant advance in the art.

The roll 41 may be rotated at a steady, slow rate, for example, R. P.M., in either direction, while the grinding wheel continues to work atnormal grinding speeds. If the shaft 26 is geared to turn 30 degrees perminute, and the threaded portion has 10 threads per inch, the wheelforming tool will advance at the rate of one-half inch per hour. Theforegoing example describes typical rates which I have found desirablefor a given set of grinding conditions.

While I have illustrated and described preferred embodiments of myinvention, the foregoing is by way of illustration only of a novel wheelforming method which radically departs from conventional practice ashereinbefore described.

I claim:

1. During a grinding operation, the method of maintaining the workingpoint on the periphery of a grinding wheel in proper relation to aworkpiece being ground, said wheel having a desired form, that comprisesgrinding said workpiece with said wheel whereby the diameter of saidwheel decreases at a determinable attrition rate, feeding substantiallyradially into said wheel a member shaped to the complement of thedesired form of said wheel at a constant, positive forming rate greaterthan said attrition rate, rotating said wheel and said member atdifferent peripheral speeds and simultaneously advancing said wheeltowards said workpiece at a rate substantially equal to said formingrate.

2. During a grinding operation, the method of maintaining the workingpoint on the periphery of a grinding wheel in proper relation to aworkpiece being ground, said Wheel having a desired form, that comprisesgrinding said workpiece with said wheel whereby the diameter of saidwheel decreases at a determinable attrition rate, feeding substantiallyradially into said wheel a member shaped to the complement of thedesired form of said wheel at a constant, positive forming rate greaterthan said attrition rate, rotating said wheel and said member atsubstantially different peripheral speeds and simultaneously advancingsaid wheel towards said workpiece at a rate substantially equal to saidforming rate.

3. A method as defined in claim 1 in which said wheel and said memberare rotating in opposite directions.

4. During a grinding operation, the method of maintaining the workingpoint on the periphery 'of a grinding wheel in proper relation to aworkpiece being ground, said wheel having a desired form, that comprisesgrinding said workpiece with said wheel whereby the diameter of saidwheel decreases at a determinable attrition rate, feeding substantiallyradially into said wheel a member shaped to the complement of thedesired form of said wheel at a constant, positive forming rate greaterthan said attrition rate, said member comprising a roll of hard abrasivematerial including diamond particles held to gether by a bondingsubstance, rotating said wheel and said member at difierent peripheralspeeds and simultaneously advancing said wheel towards said workpiece ata rate substantially equal to said forming rate.

5. The method of wheel trueing by maintaining the working point on theperiphery of a grinding wheel in proper relation to a workpiece beingground during a grinding operation, said wheel having a desired form,that comprises: grinding said workpiece with said wheel whereby thediameter of said wheel decreases at a determinable attrition rate;feeding substantially radially into said wheel a member shaped to thecomplement of the desired form of said wheel at a constant, positiveforming rate greater than said attrition rate; rotating said wheel andsaid member at difierent peripheral speeds; and simultaneously advancingsaid wheel towards said workpiece at a rate substantially equal to saidforming rate, said advance being in addition to the advance producingsaid grinding operation.

References Cited in the file of this patent or the original patentUNITED STATES PATENTS 821,621 Dunn May 29, 1906 1,126,023 Johnson Jan.26, 1915 1,313,702 Kreiger Aug. 19, 1919 1,896,533 Vuilleumier Feb. 7,1933 2,100,954 Gould Nov. 30, 1937 2,333,304 Ernst Nov. 2, 19432,347,283 Ross Apr. 25, 1944 2,576,239 Reimschissel Nov. 27, 1951FOREIGN PATENTS 610,978 Germany Mar. 20, 1936

